* Orgrim has a bigger role. We see him lead warriors, crossing paths with Anduin once. Durotan is more of a secondary character. Alonsus Faol is the counterpart to Durotan in the Alliance. Both Blackhand and Llane have fight scenes leading the troops as well, but work in secondary roles.
* Khadgar and Garona live together in Karazhan. She's particularly interested in mind control and how to protect against it.
* Multiple battles, the humans are winning, but we see there's more and more orcs crossing the portal each day.
* We see the orcs lay siege to Blackrock Spire, and slaughter the Dark Iron dwarves. Some orc leaders dislike the move far from fertile lands, which were the true goal of the campaign, but recognize the value of the fortress. In truth Gul'dan wanted the place for the magical value, and he doesn't care about his people.
* Durotan doesn't trust Gul'dan, and suspects of his true intentions. The spirits show him the corruption his race will face if he's not stopped. He warns Orgrim, but he's conflicted.
* Durotan seeks the help of the humans, not telling Orgrim about it. He wants to warn them of the dangers of demonic energy. Only the Church answers. Khadgar and Garona act as liaison between Durotan and Alonsus Faol. The Blackhand brothers lead an ambush against them, killing Durotan and a few members of each party. Garona saves Alonsus Faol from a fatal blow. Khadgar sees the demonic energy Durotan spoke about in action in the assault, and realizes it's the same he's seen Medivh use.
* Anduin, Garona, and Khadgar confront Medivh, killing him. Gul'dan suffers a backlash, and is greatly weakened by this.
* Orgrim is informed of Durotan's death. The Blackhands tell him it was the humans. He researches and finds proof of demonic energy being used in the ambush. He finds proof of the negotiations as well, and is angry at Durotan for hiding it, but now he believes his visions about Gul'dan.
* He tells Blackhand of his suspicions, but he's mocked. He notices he's just another puppet, his sons lying about Durotan's death, and he challenges him for leadership of the Horde, winning after killing him at Blackrock Spire.
* Anduin, Garona, and Khadgar come back to Stormwind.
* Orgrim assault's Gul'dan's lair, killing his servants. He then exiles the Frostwolves, sending them to scout north, both because of anger at their betrayal and to keep internal conflicts out of the Horde.
* Captured, Gul'dan pledges for his life. He offers help in weakening the defenses of Stormwind. Orgrim knows he's powerful, and gives him a last chance. Gul'dan performs a ritual, and manages to mind controls Garona, making her go crazy, killing Llane and other troops, and sabotaging vital infrastructure in the city. Khadgar senses her corruption, and tracks her, downing her. The guards believe she's dead, and Khadgar takes her back to Northshire, where Faol cleanses her corruption. A free Garona tells them a new army of orcs is coming, that she thought she could resist the mind control, and that she's sorry for hiding her true nature. Khadgar can't trust her anymore, and teleports her far away. Faol evacuates the Abbey.
* Seeing the fires over Stormwind, Orgrim knows Gul'dan did his job, and lets him live for now.
* Siege of Stormwind City, humans lose, and they flee by ship.

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Metzen: They are one of the ancient races of Northrend that we haven't spoken of before... because we hadn't made them up before. (laughter)

I don't think the film needs to be very different in order to work. It just needs that extra hour of screentime that the cast deserved.

I would have preferred Garona getting Lothar out of his funk with some method other than pity-sex in the Lions' Pride Inn.

I think Fimmel did the role well for the script that was written, but I didn't buy him having a fully-grown son, and that contributed to Callan's somewhat weak connectivity in the film. If you nix the GaronaXLothar romance from the script, you can cast Lothar as a bit older, and that helps sell Callan a bit better.

From my understanding, there was a perfect spot for Aegwyn that was given to someone random.

It's hard to tell because the pronunciation isn't what you'd expect, but Glenn Close was playing Alodi.

From a narrative standpoint, I think they were trying to put more emphasis on the office of the Guardian, which is something that Alodi is a better exemplar of than Aegwynn. I'll need to see if the novelization expands on that at all.